text: An example of a Lewis structure with no formal charge,
  illustrates that, in this algorithm, homonuclear bonds are simply ignored (the bond orders are in blue).
  Carbon monoxide exemplifies a Lewis structure with formal charges:
  To obtain the oxidation states, the formal charges are summed with the bond-order value taken positively at the carbon and negatively at the oxygen.
  Applied to molecular ions, this algorithm considers the actual location of the formal (ionic) charge, as drawn in the Lewis structure. As an example, summing bond orders in the ammonium cation yields −4 at the nitrogen of formal charge +1, with the two numbers adding to the oxidation state of −3:
  The sum of oxidation states in the ion equals its charge (as it equals zero for a neutral molecule).
  Also in anions, the formal (ionic) charges have to be considered when nonzero. For sulfate this is exemplified with the skeletal or Lewis structures (top), compared with the bond-order formula of all oxygens equivalent and fulfilling the octet and  rules (bottom):